Abstract: Aramid nanofibers (NAF) with a diameter of 40-50 nm and a length of 2-5 μm were successfully prepared by dissolving macroscopic aramid fiber (AF) in dimethyl sulfoxide(DMSO)-KOH system, and the microstructure, chemical and crystal structure of NAF and AF were analyzed by SEM, TEM, FTIR, Raman and XRD. The results show that NAF and AF have similar chemical structures, while NAF retains most of the crystalline structure of AF, only a certain difference in fiber size. NAF composite film with layered dense structure was prepared by vacuum-assisted layer-by-layer self-assembled method. The film exhibits good transparency, flexibility, temperature resistance and mechanical properties. The film also has certain lyophilic properties (contact angle is 81.5°) and excellent resistance to liquid penetration and liquid absorption.